diff options
Diffstat (limited to 'drivers/gpu/drm/i915/intel_breadcrumbs.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_breadcrumbs.c | 898 |
1 files changed, 898 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c new file mode 100644 index 000000000..1db6ba7d9 --- /dev/null +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -0,0 +1,898 @@ +/* + * Copyright © 2015 Intel Corporation + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + * + */ + +#include <linux/kthread.h> +#include <uapi/linux/sched/types.h> + +#include "i915_drv.h" + +#ifdef CONFIG_SMP +#define task_asleep(tsk) ((tsk)->state & TASK_NORMAL && !(tsk)->on_cpu) +#else +#define task_asleep(tsk) ((tsk)->state & TASK_NORMAL) +#endif + +static unsigned int __intel_breadcrumbs_wakeup(struct intel_breadcrumbs *b) +{ + struct intel_wait *wait; + unsigned int result = 0; + + lockdep_assert_held(&b->irq_lock); + + wait = b->irq_wait; + if (wait) { + /* + * N.B. Since task_asleep() and ttwu are not atomic, the + * waiter may actually go to sleep after the check, causing + * us to suppress a valid wakeup. We prefer to reduce the + * number of false positive missed_breadcrumb() warnings + * at the expense of a few false negatives, as it it easy + * to trigger a false positive under heavy load. Enough + * signal should remain from genuine missed_breadcrumb() + * for us to detect in CI. + */ + bool was_asleep = task_asleep(wait->tsk); + + result = ENGINE_WAKEUP_WAITER; + if (wake_up_process(wait->tsk) && was_asleep) + result |= ENGINE_WAKEUP_ASLEEP; + } + + return result; +} + +unsigned int intel_engine_wakeup(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + unsigned long flags; + unsigned int result; + + spin_lock_irqsave(&b->irq_lock, flags); + result = __intel_breadcrumbs_wakeup(b); + spin_unlock_irqrestore(&b->irq_lock, flags); + + return result; +} + +static unsigned long wait_timeout(void) +{ + return round_jiffies_up(jiffies + DRM_I915_HANGCHECK_JIFFIES); +} + +static noinline void missed_breadcrumb(struct intel_engine_cs *engine) +{ + if (GEM_SHOW_DEBUG()) { + struct drm_printer p = drm_debug_printer(__func__); + + intel_engine_dump(engine, &p, + "%s missed breadcrumb at %pS\n", + engine->name, __builtin_return_address(0)); + } + + set_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings); +} + +static void intel_breadcrumbs_hangcheck(struct timer_list *t) +{ + struct intel_engine_cs *engine = + from_timer(engine, t, breadcrumbs.hangcheck); + struct intel_breadcrumbs *b = &engine->breadcrumbs; + unsigned int irq_count; + + if (!b->irq_armed) + return; + + irq_count = READ_ONCE(b->irq_count); + if (b->hangcheck_interrupts != irq_count) { + b->hangcheck_interrupts = irq_count; + mod_timer(&b->hangcheck, wait_timeout()); + return; + } + + /* We keep the hangcheck timer alive until we disarm the irq, even + * if there are no waiters at present. + * + * If the waiter was currently running, assume it hasn't had a chance + * to process the pending interrupt (e.g, low priority task on a loaded + * system) and wait until it sleeps before declaring a missed interrupt. + * + * If the waiter was asleep (and not even pending a wakeup), then we + * must have missed an interrupt as the GPU has stopped advancing + * but we still have a waiter. Assuming all batches complete within + * DRM_I915_HANGCHECK_JIFFIES [1.5s]! + */ + if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP) { + missed_breadcrumb(engine); + mod_timer(&b->fake_irq, jiffies + 1); + } else { + mod_timer(&b->hangcheck, wait_timeout()); + } +} + +static void intel_breadcrumbs_fake_irq(struct timer_list *t) +{ + struct intel_engine_cs *engine = + from_timer(engine, t, breadcrumbs.fake_irq); + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + /* + * The timer persists in case we cannot enable interrupts, + * or if we have previously seen seqno/interrupt incoherency + * ("missed interrupt" syndrome, better known as a "missed breadcrumb"). + * Here the worker will wake up every jiffie in order to kick the + * oldest waiter to do the coherent seqno check. + */ + + spin_lock_irq(&b->irq_lock); + if (b->irq_armed && !__intel_breadcrumbs_wakeup(b)) + __intel_engine_disarm_breadcrumbs(engine); + spin_unlock_irq(&b->irq_lock); + if (!b->irq_armed) + return; + + /* If the user has disabled the fake-irq, restore the hangchecking */ + if (!test_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings)) { + mod_timer(&b->hangcheck, wait_timeout()); + return; + } + + mod_timer(&b->fake_irq, jiffies + 1); +} + +static void irq_enable(struct intel_engine_cs *engine) +{ + /* + * FIXME: Ideally we want this on the API boundary, but for the + * sake of testing with mock breadcrumbs (no HW so unable to + * enable irqs) we place it deep within the bowels, at the point + * of no return. + */ + GEM_BUG_ON(!intel_irqs_enabled(engine->i915)); + + /* Enabling the IRQ may miss the generation of the interrupt, but + * we still need to force the barrier before reading the seqno, + * just in case. + */ + set_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted); + + /* Caller disables interrupts */ + if (engine->irq_enable) { + spin_lock(&engine->i915->irq_lock); + engine->irq_enable(engine); + spin_unlock(&engine->i915->irq_lock); + } +} + +static void irq_disable(struct intel_engine_cs *engine) +{ + /* Caller disables interrupts */ + if (engine->irq_disable) { + spin_lock(&engine->i915->irq_lock); + engine->irq_disable(engine); + spin_unlock(&engine->i915->irq_lock); + } +} + +void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + lockdep_assert_held(&b->irq_lock); + GEM_BUG_ON(b->irq_wait); + GEM_BUG_ON(!b->irq_armed); + + GEM_BUG_ON(!b->irq_enabled); + if (!--b->irq_enabled) + irq_disable(engine); + + b->irq_armed = false; +} + +void intel_engine_pin_breadcrumbs_irq(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + spin_lock_irq(&b->irq_lock); + if (!b->irq_enabled++) + irq_enable(engine); + GEM_BUG_ON(!b->irq_enabled); /* no overflow! */ + spin_unlock_irq(&b->irq_lock); +} + +void intel_engine_unpin_breadcrumbs_irq(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + spin_lock_irq(&b->irq_lock); + GEM_BUG_ON(!b->irq_enabled); /* no underflow! */ + if (!--b->irq_enabled) + irq_disable(engine); + spin_unlock_irq(&b->irq_lock); +} + +void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct intel_wait *wait, *n; + + if (!b->irq_armed) + return; + + /* + * We only disarm the irq when we are idle (all requests completed), + * so if the bottom-half remains asleep, it missed the request + * completion. + */ + if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP) + missed_breadcrumb(engine); + + spin_lock_irq(&b->rb_lock); + + spin_lock(&b->irq_lock); + b->irq_wait = NULL; + if (b->irq_armed) + __intel_engine_disarm_breadcrumbs(engine); + spin_unlock(&b->irq_lock); + + rbtree_postorder_for_each_entry_safe(wait, n, &b->waiters, node) { + GEM_BUG_ON(!i915_seqno_passed(intel_engine_get_seqno(engine), + wait->seqno)); + RB_CLEAR_NODE(&wait->node); + wake_up_process(wait->tsk); + } + b->waiters = RB_ROOT; + + spin_unlock_irq(&b->rb_lock); +} + +static bool use_fake_irq(const struct intel_breadcrumbs *b) +{ + const struct intel_engine_cs *engine = + container_of(b, struct intel_engine_cs, breadcrumbs); + + if (!test_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings)) + return false; + + /* + * Only start with the heavy weight fake irq timer if we have not + * seen any interrupts since enabling it the first time. If the + * interrupts are still arriving, it means we made a mistake in our + * engine->seqno_barrier(), a timing error that should be transient + * and unlikely to reoccur. + */ + return READ_ONCE(b->irq_count) == b->hangcheck_interrupts; +} + +static void enable_fake_irq(struct intel_breadcrumbs *b) +{ + /* Ensure we never sleep indefinitely */ + if (!b->irq_enabled || use_fake_irq(b)) + mod_timer(&b->fake_irq, jiffies + 1); + else + mod_timer(&b->hangcheck, wait_timeout()); +} + +static bool __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b) +{ + struct intel_engine_cs *engine = + container_of(b, struct intel_engine_cs, breadcrumbs); + struct drm_i915_private *i915 = engine->i915; + bool enabled; + + lockdep_assert_held(&b->irq_lock); + if (b->irq_armed) + return false; + + /* The breadcrumb irq will be disarmed on the interrupt after the + * waiters are signaled. This gives us a single interrupt window in + * which we can add a new waiter and avoid the cost of re-enabling + * the irq. + */ + b->irq_armed = true; + + if (I915_SELFTEST_ONLY(b->mock)) { + /* For our mock objects we want to avoid interaction + * with the real hardware (which is not set up). So + * we simply pretend we have enabled the powerwell + * and the irq, and leave it up to the mock + * implementation to call intel_engine_wakeup() + * itself when it wants to simulate a user interrupt, + */ + return true; + } + + /* Since we are waiting on a request, the GPU should be busy + * and should have its own rpm reference. This is tracked + * by i915->gt.awake, we can forgo holding our own wakref + * for the interrupt as before i915->gt.awake is released (when + * the driver is idle) we disarm the breadcrumbs. + */ + + /* No interrupts? Kick the waiter every jiffie! */ + enabled = false; + if (!b->irq_enabled++ && + !test_bit(engine->id, &i915->gpu_error.test_irq_rings)) { + irq_enable(engine); + enabled = true; + } + + enable_fake_irq(b); + return enabled; +} + +static inline struct intel_wait *to_wait(struct rb_node *node) +{ + return rb_entry(node, struct intel_wait, node); +} + +static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b, + struct intel_wait *wait) +{ + lockdep_assert_held(&b->rb_lock); + GEM_BUG_ON(b->irq_wait == wait); + + /* + * This request is completed, so remove it from the tree, mark it as + * complete, and *then* wake up the associated task. N.B. when the + * task wakes up, it will find the empty rb_node, discern that it + * has already been removed from the tree and skip the serialisation + * of the b->rb_lock and b->irq_lock. This means that the destruction + * of the intel_wait is not serialised with the interrupt handler + * by the waiter - it must instead be serialised by the caller. + */ + rb_erase(&wait->node, &b->waiters); + RB_CLEAR_NODE(&wait->node); + + if (wait->tsk->state != TASK_RUNNING) + wake_up_process(wait->tsk); /* implicit smp_wmb() */ +} + +static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine, + struct rb_node *next) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + spin_lock(&b->irq_lock); + GEM_BUG_ON(!b->irq_armed); + GEM_BUG_ON(!b->irq_wait); + b->irq_wait = to_wait(next); + spin_unlock(&b->irq_lock); + + /* We always wake up the next waiter that takes over as the bottom-half + * as we may delegate not only the irq-seqno barrier to the next waiter + * but also the task of waking up concurrent waiters. + */ + if (next) + wake_up_process(to_wait(next)->tsk); +} + +static bool __intel_engine_add_wait(struct intel_engine_cs *engine, + struct intel_wait *wait) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct rb_node **p, *parent, *completed; + bool first, armed; + u32 seqno; + + GEM_BUG_ON(!wait->seqno); + + /* Insert the request into the retirement ordered list + * of waiters by walking the rbtree. If we are the oldest + * seqno in the tree (the first to be retired), then + * set ourselves as the bottom-half. + * + * As we descend the tree, prune completed branches since we hold the + * spinlock we know that the first_waiter must be delayed and can + * reduce some of the sequential wake up latency if we take action + * ourselves and wake up the completed tasks in parallel. Also, by + * removing stale elements in the tree, we may be able to reduce the + * ping-pong between the old bottom-half and ourselves as first-waiter. + */ + armed = false; + first = true; + parent = NULL; + completed = NULL; + seqno = intel_engine_get_seqno(engine); + + /* If the request completed before we managed to grab the spinlock, + * return now before adding ourselves to the rbtree. We let the + * current bottom-half handle any pending wakeups and instead + * try and get out of the way quickly. + */ + if (i915_seqno_passed(seqno, wait->seqno)) { + RB_CLEAR_NODE(&wait->node); + return first; + } + + p = &b->waiters.rb_node; + while (*p) { + parent = *p; + if (wait->seqno == to_wait(parent)->seqno) { + /* We have multiple waiters on the same seqno, select + * the highest priority task (that with the smallest + * task->prio) to serve as the bottom-half for this + * group. + */ + if (wait->tsk->prio > to_wait(parent)->tsk->prio) { + p = &parent->rb_right; + first = false; + } else { + p = &parent->rb_left; + } + } else if (i915_seqno_passed(wait->seqno, + to_wait(parent)->seqno)) { + p = &parent->rb_right; + if (i915_seqno_passed(seqno, to_wait(parent)->seqno)) + completed = parent; + else + first = false; + } else { + p = &parent->rb_left; + } + } + rb_link_node(&wait->node, parent, p); + rb_insert_color(&wait->node, &b->waiters); + + if (first) { + spin_lock(&b->irq_lock); + b->irq_wait = wait; + /* After assigning ourselves as the new bottom-half, we must + * perform a cursory check to prevent a missed interrupt. + * Either we miss the interrupt whilst programming the hardware, + * or if there was a previous waiter (for a later seqno) they + * may be woken instead of us (due to the inherent race + * in the unlocked read of b->irq_seqno_bh in the irq handler) + * and so we miss the wake up. + */ + armed = __intel_breadcrumbs_enable_irq(b); + spin_unlock(&b->irq_lock); + } + + if (completed) { + /* Advance the bottom-half (b->irq_wait) before we wake up + * the waiters who may scribble over their intel_wait + * just as the interrupt handler is dereferencing it via + * b->irq_wait. + */ + if (!first) { + struct rb_node *next = rb_next(completed); + GEM_BUG_ON(next == &wait->node); + __intel_breadcrumbs_next(engine, next); + } + + do { + struct intel_wait *crumb = to_wait(completed); + completed = rb_prev(completed); + __intel_breadcrumbs_finish(b, crumb); + } while (completed); + } + + GEM_BUG_ON(!b->irq_wait); + GEM_BUG_ON(!b->irq_armed); + GEM_BUG_ON(rb_first(&b->waiters) != &b->irq_wait->node); + + return armed; +} + +bool intel_engine_add_wait(struct intel_engine_cs *engine, + struct intel_wait *wait) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + bool armed; + + spin_lock_irq(&b->rb_lock); + armed = __intel_engine_add_wait(engine, wait); + spin_unlock_irq(&b->rb_lock); + if (armed) + return armed; + + /* Make the caller recheck if its request has already started. */ + return i915_seqno_passed(intel_engine_get_seqno(engine), + wait->seqno - 1); +} + +static inline bool chain_wakeup(struct rb_node *rb, int priority) +{ + return rb && to_wait(rb)->tsk->prio <= priority; +} + +static inline int wakeup_priority(struct intel_breadcrumbs *b, + struct task_struct *tsk) +{ + if (tsk == b->signaler) + return INT_MIN; + else + return tsk->prio; +} + +static void __intel_engine_remove_wait(struct intel_engine_cs *engine, + struct intel_wait *wait) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + lockdep_assert_held(&b->rb_lock); + + if (RB_EMPTY_NODE(&wait->node)) + goto out; + + if (b->irq_wait == wait) { + const int priority = wakeup_priority(b, wait->tsk); + struct rb_node *next; + + /* We are the current bottom-half. Find the next candidate, + * the first waiter in the queue on the remaining oldest + * request. As multiple seqnos may complete in the time it + * takes us to wake up and find the next waiter, we have to + * wake up that waiter for it to perform its own coherent + * completion check. + */ + next = rb_next(&wait->node); + if (chain_wakeup(next, priority)) { + /* If the next waiter is already complete, + * wake it up and continue onto the next waiter. So + * if have a small herd, they will wake up in parallel + * rather than sequentially, which should reduce + * the overall latency in waking all the completed + * clients. + * + * However, waking up a chain adds extra latency to + * the first_waiter. This is undesirable if that + * waiter is a high priority task. + */ + u32 seqno = intel_engine_get_seqno(engine); + + while (i915_seqno_passed(seqno, to_wait(next)->seqno)) { + struct rb_node *n = rb_next(next); + + __intel_breadcrumbs_finish(b, to_wait(next)); + next = n; + if (!chain_wakeup(next, priority)) + break; + } + } + + __intel_breadcrumbs_next(engine, next); + } else { + GEM_BUG_ON(rb_first(&b->waiters) == &wait->node); + } + + GEM_BUG_ON(RB_EMPTY_NODE(&wait->node)); + rb_erase(&wait->node, &b->waiters); + RB_CLEAR_NODE(&wait->node); + +out: + GEM_BUG_ON(b->irq_wait == wait); + GEM_BUG_ON(rb_first(&b->waiters) != + (b->irq_wait ? &b->irq_wait->node : NULL)); +} + +void intel_engine_remove_wait(struct intel_engine_cs *engine, + struct intel_wait *wait) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + /* Quick check to see if this waiter was already decoupled from + * the tree by the bottom-half to avoid contention on the spinlock + * by the herd. + */ + if (RB_EMPTY_NODE(&wait->node)) { + GEM_BUG_ON(READ_ONCE(b->irq_wait) == wait); + return; + } + + spin_lock_irq(&b->rb_lock); + __intel_engine_remove_wait(engine, wait); + spin_unlock_irq(&b->rb_lock); +} + +static void signaler_set_rtpriority(void) +{ + struct sched_param param = { .sched_priority = 1 }; + + sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m); +} + +static int intel_breadcrumbs_signaler(void *arg) +{ + struct intel_engine_cs *engine = arg; + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct i915_request *rq, *n; + + /* Install ourselves with high priority to reduce signalling latency */ + signaler_set_rtpriority(); + + do { + bool do_schedule = true; + LIST_HEAD(list); + u32 seqno; + + set_current_state(TASK_INTERRUPTIBLE); + if (list_empty(&b->signals)) + goto sleep; + + /* + * We are either woken up by the interrupt bottom-half, + * or by a client adding a new signaller. In both cases, + * the GPU seqno may have advanced beyond our oldest signal. + * If it has, propagate the signal, remove the waiter and + * check again with the next oldest signal. Otherwise we + * need to wait for a new interrupt from the GPU or for + * a new client. + */ + seqno = intel_engine_get_seqno(engine); + + spin_lock_irq(&b->rb_lock); + list_for_each_entry_safe(rq, n, &b->signals, signaling.link) { + u32 this = rq->signaling.wait.seqno; + + GEM_BUG_ON(!rq->signaling.wait.seqno); + + if (!i915_seqno_passed(seqno, this)) + break; + + if (likely(this == i915_request_global_seqno(rq))) { + __intel_engine_remove_wait(engine, + &rq->signaling.wait); + + rq->signaling.wait.seqno = 0; + __list_del_entry(&rq->signaling.link); + + if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, + &rq->fence.flags)) { + list_add_tail(&rq->signaling.link, + &list); + i915_request_get(rq); + } + } + } + spin_unlock_irq(&b->rb_lock); + + if (!list_empty(&list)) { + local_bh_disable(); + list_for_each_entry_safe(rq, n, &list, signaling.link) { + dma_fence_signal(&rq->fence); + GEM_BUG_ON(!i915_request_completed(rq)); + i915_request_put(rq); + } + local_bh_enable(); /* kick start the tasklets */ + + /* + * If the engine is saturated we may be continually + * processing completed requests. This angers the + * NMI watchdog if we never let anything else + * have access to the CPU. Let's pretend to be nice + * and relinquish the CPU if we burn through the + * entire RT timeslice! + */ + do_schedule = need_resched(); + } + + if (unlikely(do_schedule)) { + /* Before we sleep, check for a missed seqno */ + if (current->state & TASK_NORMAL && + !list_empty(&b->signals) && + engine->irq_seqno_barrier && + test_and_clear_bit(ENGINE_IRQ_BREADCRUMB, + &engine->irq_posted)) { + engine->irq_seqno_barrier(engine); + intel_engine_wakeup(engine); + } + +sleep: + if (kthread_should_park()) + kthread_parkme(); + + if (unlikely(kthread_should_stop())) + break; + + schedule(); + } + } while (1); + __set_current_state(TASK_RUNNING); + + return 0; +} + +static void insert_signal(struct intel_breadcrumbs *b, + struct i915_request *request, + const u32 seqno) +{ + struct i915_request *iter; + + lockdep_assert_held(&b->rb_lock); + + /* + * A reasonable assumption is that we are called to add signals + * in sequence, as the requests are submitted for execution and + * assigned a global_seqno. This will be the case for the majority + * of internally generated signals (inter-engine signaling). + * + * Out of order waiters triggering random signaling enabling will + * be more problematic, but hopefully rare enough and the list + * small enough that the O(N) insertion sort is not an issue. + */ + + list_for_each_entry_reverse(iter, &b->signals, signaling.link) + if (i915_seqno_passed(seqno, iter->signaling.wait.seqno)) + break; + + list_add(&request->signaling.link, &iter->signaling.link); +} + +bool intel_engine_enable_signaling(struct i915_request *request, bool wakeup) +{ + struct intel_engine_cs *engine = request->engine; + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct intel_wait *wait = &request->signaling.wait; + u32 seqno; + + /* + * Note that we may be called from an interrupt handler on another + * device (e.g. nouveau signaling a fence completion causing us + * to submit a request, and so enable signaling). As such, + * we need to make sure that all other users of b->rb_lock protect + * against interrupts, i.e. use spin_lock_irqsave. + */ + + /* locked by dma_fence_enable_sw_signaling() (irqsafe fence->lock) */ + GEM_BUG_ON(!irqs_disabled()); + lockdep_assert_held(&request->lock); + + seqno = i915_request_global_seqno(request); + if (!seqno) /* will be enabled later upon execution */ + return true; + + GEM_BUG_ON(wait->seqno); + wait->tsk = b->signaler; + wait->request = request; + wait->seqno = seqno; + + /* + * Add ourselves into the list of waiters, but registering our + * bottom-half as the signaller thread. As per usual, only the oldest + * waiter (not just signaller) is tasked as the bottom-half waking + * up all completed waiters after the user interrupt. + * + * If we are the oldest waiter, enable the irq (after which we + * must double check that the seqno did not complete). + */ + spin_lock(&b->rb_lock); + insert_signal(b, request, seqno); + wakeup &= __intel_engine_add_wait(engine, wait); + spin_unlock(&b->rb_lock); + + if (wakeup) { + wake_up_process(b->signaler); + return !intel_wait_complete(wait); + } + + return true; +} + +void intel_engine_cancel_signaling(struct i915_request *request) +{ + struct intel_engine_cs *engine = request->engine; + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + GEM_BUG_ON(!irqs_disabled()); + lockdep_assert_held(&request->lock); + + if (!READ_ONCE(request->signaling.wait.seqno)) + return; + + spin_lock(&b->rb_lock); + __intel_engine_remove_wait(engine, &request->signaling.wait); + if (fetch_and_zero(&request->signaling.wait.seqno)) + __list_del_entry(&request->signaling.link); + spin_unlock(&b->rb_lock); +} + +int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + struct task_struct *tsk; + + spin_lock_init(&b->rb_lock); + spin_lock_init(&b->irq_lock); + + timer_setup(&b->fake_irq, intel_breadcrumbs_fake_irq, 0); + timer_setup(&b->hangcheck, intel_breadcrumbs_hangcheck, 0); + + INIT_LIST_HEAD(&b->signals); + + /* Spawn a thread to provide a common bottom-half for all signals. + * As this is an asynchronous interface we cannot steal the current + * task for handling the bottom-half to the user interrupt, therefore + * we create a thread to do the coherent seqno dance after the + * interrupt and then signal the waitqueue (via the dma-buf/fence). + */ + tsk = kthread_run(intel_breadcrumbs_signaler, engine, + "i915/signal:%d", engine->id); + if (IS_ERR(tsk)) + return PTR_ERR(tsk); + + b->signaler = tsk; + + return 0; +} + +static void cancel_fake_irq(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + del_timer_sync(&b->fake_irq); /* may queue b->hangcheck */ + del_timer_sync(&b->hangcheck); + clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings); +} + +void intel_engine_reset_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + unsigned long flags; + + spin_lock_irqsave(&b->irq_lock, flags); + + /* + * Leave the fake_irq timer enabled (if it is running), but clear the + * bit so that it turns itself off on its next wake up and goes back + * to the long hangcheck interval if still required. + */ + clear_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings); + + if (b->irq_enabled) + irq_enable(engine); + else + irq_disable(engine); + + /* + * We set the IRQ_BREADCRUMB bit when we enable the irq presuming the + * GPU is active and may have already executed the MI_USER_INTERRUPT + * before the CPU is ready to receive. However, the engine is currently + * idle (we haven't started it yet), there is no possibility for a + * missed interrupt as we enabled the irq and so we can clear the + * immediate wakeup (until a real interrupt arrives for the waiter). + */ + clear_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted); + + spin_unlock_irqrestore(&b->irq_lock, flags); +} + +void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine) +{ + struct intel_breadcrumbs *b = &engine->breadcrumbs; + + /* The engines should be idle and all requests accounted for! */ + WARN_ON(READ_ONCE(b->irq_wait)); + WARN_ON(!RB_EMPTY_ROOT(&b->waiters)); + WARN_ON(!list_empty(&b->signals)); + + if (!IS_ERR_OR_NULL(b->signaler)) + kthread_stop(b->signaler); + + cancel_fake_irq(engine); +} + +#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST) +#include "selftests/intel_breadcrumbs.c" +#endif |